At present, mobile networks, including a Global System for Mobile communications (GSM), a Universal Mobile Telecommunications System (UMTS), employ a circuit switching technology, called a Circuit Switched (CS) domain, to provide a user with a basic voice service and supplementary services based on a voice service. When a CS domain accesses an IMS, the CS domain evolves into an access mode and its services are uniformly provided by the IMS, and this mode is called IMS centralized service.
FIG. 1 is a schematic diagram illustrating an application scenario of IMS centralized service in an existing technology. As shown in FIG. 1, an IMS User Equipment (IMS UE) 101 accesses an IMS 105 via a packet switched domain access network 102 and obtains services provided by the IMS network. By adopting the IMS centralized service technology, a CS User Equipment (CS UE) 103 accesses the IMS105 via a CS domain access network 104 and obtains services provided by the IMS network, then the IMS network can provide services for users employing different access modes.
FIG. 2 is an architecture diagram illustrating IMS centralized control service in an existing technology, which comprises the following network elements as shown in FIG. 2:
a CS UE 201, which accesses an enhanced Mobile Switch Center Server (eMSC Server) via CS control signaling;
an eMSC Server 202, which is an enhanced CS MSC Server, completes CS UE access, mobile management and call control, and additionally, serving as a Session Initiation Protocol (SIP) user agent, realizes a conversion between CS signaling and an SIP message and accesses an IMS instead of the user;
a Media Gateway (MGW) 203, for making a conversion between a media stream on a CS bearer and a media stream on an IP bearer and establishing a media connection between the CS UE 201 and a remote user;
a Call Session Control Function (CSCF) 204, which may be divided into an Interrogating CSCF (I-CSCF) and a Serving CSCF (S-CSCF), wherein the I-CSCF interacts with a Home Subscriber Server (HSS) to request the HSS to allocate an S-CSCF to the user or to interrogate which S-CSCF serves the user; wherein the S-CSCF is used for providing registration, call control and other functions for the user;
an Application Server (AS) 205, which comprises a service continuity application server and a telephone service application server, and so on, and provides the user with service including service continuity and telephone service;
an HSS/Home Location Register (HLR) 206, for storing subscription data of the user and providing supports for a call or session, wherein the HLR can be considered as a subset of the HSS and serves the conventional CS domain and packet switched domain, in a practical application, the HLR and HSS can be integrated and located in the same physical entity, and also can be located in different entities; when the HLR and HSS are located in different entities, an interface may be provided between them for realizing information exchange.
The CS UE 201 accesses the eMSC Server 202 via CS control signaling, the eMSC Server 202, serving as a user agent, instead of the user, accesses the CSCF 204 of the IMS network and establishes a session connection with the remote user, meanwhile, the eMSC Server 202 controls the MGW 203 to complete the conversion between the media stream on the CS bearer and the media stream on the IP bearer and establishes a media connection between the CS UE 201 and the remote user.
After the CS UE is successfully attached to the eMSC Server and successfully registers in the IMS via the eMSC Server which is a source MSC Server, when the CS UE moves, it may move into the control area of a new MSC Server, namely, a target MSC Server, wherein the target MSC Server may be a common MSC Server, namely an MSC server with no capacity of adding IMS centralized service, and also may be an eMSC server.
When the target MSC Server is an eMSC server, a current registration process is as shown in FIG. 3, for the sake of conciseness, the flow in FIG. 3 mainly illustrates a CS domain location update process and an IMS registration process, and no description will be given for other processes, such as security authentication and CS user data insertion; as shown in FIG. 3, the process mainly comprises the following steps.
Step 301, the UE initiates a CS attachment process and sends an attachment request to the target eMSC Server.
Step 302, the target eMSC Server sends a location update request to the HSS/HLR.
Step 303, the HSS/HLR accepts the location update and returns a location update accept response to the target eMSC server.
In a specific operation, standard CS access authentication and user data insertion are further performed in steps 302-303, and the HSS/HLR can insert an IMS centralized service indication into the user data or the location update accept response to illuminate that the user has subscribed the IMS centralized service.
Step 304, the target eMSC Server returns a CS attachment accept response to the UE.
As the target MSC Server is specifically a target eMSC Server here, therefore the target eMSC Server may check the IMS centralized service indication in the user data or location update accept response, or determines whether the user is an IMS centralized service user according to a locally configured filter rule, if the user is determined to be an IMS centralized service user, step 308 will be executed and the target eMSC Server will perform an IMS registration process instead of the UE.
Step 305, the HSS/HLR sends a location cancelling request to the source eMSC Server.
Step 306, the source eMSC Server returns a location cancelling response to the HSS/HLR and deletes a locally stored CS user record.
Step 307, the source eMSC Server performs an IMS de-registration process instead of the CS UE.
As the CS UE is not in an activated state any more in the source eMSC Server, therefore the source eMSC Server performs the IMS de-registration process instead of the CS UE and sends a de-registration request to the S-CSCF, and the S-CSCF deletes an old registration binding relationship, namely, deleting the relationship between a private user identity, a public user identity and the contact address of the source eMSC Server.
Step 308, the target eMSC server initiates the registration process of the IMS centralized service instead of the UE, after the user successfully completes the location update in the target eMSC Server, the target eMSC Server performs the IMS registration process instead of the UE, the target eMSC Server sends a registration request to the S-CSCF in the IMS, and the S-CSCF establishes a new registration binding relationship, namely establishing a relationship between a private user identity, a public user identity and the contact address of the target eMSC Server, thereby the IMS updates the registration binding relationship.
It is known from the above flow that the sequence of the registration request sent by the target eMSC server and the de-registration request sent by the source eMSC server arriving at the S-CSCF cannot be determined because the registration process initiated by the target eMSC Server and the de-registration process initiated by the source eMSC Server are performed independently, and practically, following two cases may be included as to the sequence of the registration request sent by the target eMSC server and the de-registration request sent by the source eMSC server arriving at the S-CSCF:
(1) if the de-registration request arrives at the S-CSCF earlier than the registration request, the S-CSCF first performs the de-registration process and deletes existing registration information, then reestablishes a new registration relationship when the registration request arrives at the S-CSCF; it can be learned that although there is no problem with the service logic, the de-registration process therein is not necessary, and the system efficiency is consequently influenced, moreover, after the de-registration process, the S-CSCF may release all the user data, as a result, the S-CSCF needs to redownload the user data in a new registration process, which causes redundant signaling and thereby affects the efficiency of the S-CSCF and the HSS; in addition, after the de-registration is completed, the HSS may allocate a new S-CSCF or the I-CSCF may reselect a new S-CSCF when a new registration is performed, which results in the S-CSCF being changed, furthermore, the S-CSCF may perform a third party registration/de-registration process and inform the AS of the registration information of the user, which affects the processing efficiency of the AS and may cause anomalies;
(2) if the registration request arrives at the S-CSCF earlier than the de-registration request, then the S-CSCF performs a registration process to replace the old registration relationship with a new one, subsequently, the de-registration request arrives at the S-CSCF, the S-CSCF finds out a new registration relationship by matching the user information in the de-registration request with the existing registration relationship, and further compares the contact addresses of the eMSC Servers, and rejects the de-registration request of the source eMSC Server which process is served as an exception handling process if the contact addresses are found to be different; and the source eMSC Server deletes local IMS registration data after receiving the refusal of the request; therefore, in this case, no service logic error is generated, wherein the user information in the de-registration request includes a private user identity and a public user identity.
From the above analysis it can be seen that the system processing efficiency may be affected due to the redundant signaling that may be generated if the de-registration request sent by the source eMSC Server arrives at the S-CSCF earlier than the registration request sent by the target eMSC Server.